PSI - Issue 11

M. Poiani et al. / Procedia Structural Integrity 11 (2018) 314–321 "Poiani et al." / Structural Integrity Procedia 00 (2018) 000–000 epicentre close to Norcia (Perugia province) and with a magnitude M w = 5.5. These events caused a total of 299 fatalities, 386 injured and about 4800 homeless (Fiorentino et al., 2018; Italian Department of Civil Protection, 2017). On 26 th October, there were two strong aftershocks with 5.6 and 6.1 M w . The earthquake of 30 th October, which happened at 07:40 am with M w 6.5, is the largest event in terms of released energy occurred in Italy since the M w 6.9 in 1980 during the Irpinia earthquake and, after this quake, many small towns were heavily damaged (Clementi et al., 2016b; F. Clementi et al., 2017b, 2017c). Finally, on 18 th January 2017 took place a new sequence of four strong shocks of M w =5 and epicentres located between the cities of Montereale, Capitignano and Cagnano Amiterno. Icon of damage and destruction of a long sequence of strong earthquakes of 2016-2017 is the Amatrice civic clock tower which will be investigated in this paper. Two advanced numerical models are here utilised to have an insight into the modalities of progressive damage and to provide a picture of the actual behaviour of the structure. 2. The Amatrice clock tower: historical and geometrical surveys Symbol of the city of Amatrice (Rieti, Italy), the Civic Tower (Fig. 1) rises in Cacciatori del Tevere square, underlining the crossroads of two main streets of the city centre, Via Roma and Corso Umberto I. There are few historical data about the Civic Tower, its origins are placed back to medieval times, as early as 1293 it was mentioned in ancient documents. Originally the clock tower was connected to the Church of Santa Lucia, demolished in 1684 by the feudal "lord" Alessandro Maria Orsini: on this occasion, the base of the tower was reinforced and a small annex was added on two sides. The last and probably the only consolidation intervention was carried out on the tower in 1979, when, following the earthquake of the Alta Valnerina (central Italy), significant damage was noticed to the tower. In 1985 the original bell of 1494 was replaced because it had undergone a crack during the restoration phases: a lighter one has been inserted in the tower to avoid high oscillations as in the past. From a geometrical point of view, the civic tower of Amatrice has a rectangular plan of 4.00 m x 5.30 m and a height of about 25 m. At the base, there is a small overhang leaning only two walls, to east elevation with a depth of 1.5 m, and to north elevation with a depth of 0.60 m. The annex houses the staircase leading to the entrance of upper floors. In its vertical development there are three distinct areas marked by the reduction of the wall thickness. The first floor is located at about 9 m in height and it is composed of smoothed stones on the outer side, falling 15 centimeters in the wall thickness, while the second frame is located at the height of about 19 meters and it marks the passageway from the tower to the belfry. In its highest part, there is the bell cell which develops longitudinally for just over 5 m: it consists of 4 regular piers with dimension 0.90 m x 0.80 m and with same openings on the opposite sides (see Fig. 1). In the top, Amatrice clock tower has a wooden pavilion roof. 315 2

Fig. 1. Main façades of Civic Tower of Amatrice and historical photos of Corso Umberto I.